I need some help with a sump

[warrenmichaels]

I started a thread recently (link at end) dealing with sumps. I'm going to have to change things; maybe someone can offer a suggestion.

I have a 90 gal tank and an (as yet) undrilled 20 gallon long for a sump. The 90 gal in on a stand, so that the bottom of the tank is about 2 ft above the ground. This is not a tank for display, but for keeping things alive, so it's OK if it doesn't look the best.

In the 90 gal tank, I've already drilled two holes (unfortunately). This limits me somewhat. Water will circuit from the DT to SUMP to RETURN PUMP to CHILLER (just in the summer), and back to the tank. A broad estimate, assuming I have one line leaving the tank and one line returning, is that I might have 15' of tubing of between 3/4" and 1" above the sump. I will have an ATO with five gallons of water and a kalkwasser addition pump drawing from a 0.5 gal pail feeding into the sump.

So, if there is failure of some sort, an absolute worst case scenario is that I'll have DT, lines, 5 gallon water, and 0.5 gallon water draining into the tank.

I'm planning to keep the water level low enough in the DT that if the drain should fail, all of the water from the sump, plus the 5 gallon ATO and the 0.5 kalkwasser can all be pumped into the DT without incident.

Having enough volume in the sump for the draining of the DT, lines, 5 gal bucket, and 0.5 gallon pail is where things get tricky.

If I have no weir in the tank, I can plumb two drain lines using a Herbie style of sorts. The primary pipe can enter the tank and turn downward. The secondary pipe can turn upward. The water will flow through the primary as a siphon, and trickle through the secondary.

If I do this, I wonder if I should take the volume of the secondary line into consideration regarding how much volume the sump can hold. My gut feeling is that I should not, or should I?

In such a scenario, I'll have 1" height difference between the two drain pipes. Assuming that the water level will be slightly over the secondary pipe, This gives me 999 cubic inches, or 4.3 gallons.

This can work if I make some changes/compromises, but I'm not sure what I should change.

All of the above factors (assuming I take into account the volume of the primary drain line, the return line and NOT the secondary drain line) would sum to a volume potentially entering the sump of 2416 cubic inches (10.5 gallons). If I have the sump configured with a skimmer depth of 6.5" over 14 horizontal inches, the rest of the sump would have to be at 2.5" depth. This is JUST enough space to accommodate all of the above-mentioned water with absolutely no head to spare. If the water were to drop much at all, the return pump would not be supplied with water.

So, if I stick with things as they are, all will be fine so long as my ATO doesn't fail. This all supposes that I don't have to take the volume of the secondary drain into consideration.

Another option is to decrease the already small height difference between my primary and secondary drain. I can decrease the potential loss from the DT tank by 200 in^3 (0.9 gallons) for every 1/4" of height difference I remove.


Another option is to get a larger sump.

Another option is not to worry about all of the sources of water that I mentioned. It is, after all, unlikely that my ATO would fail in the ON position while the return pump has failed in the OFF position. This would save me from worrying about 5 gallons!

I could install a weir so that the maximum water I'd have to worry about leaving the tank would be the height that comes over the weir, which would be about 0.25" max, or 200 in^3 (0.9 gallons). This would save me from worrying about 3.5 gallons!

So, what solution, or combination of solutions should I choose? Should I worry about the volume of the secondary drain line?

Thanks

http://reefcentral.com/forums/showthread.php?t=2688584

 

[warrenmichaels]

One final option is to lower the depth of the sump in which the skimmer rests to 6" from 6.5. Mcgyvr mentioned in another post that 6.5" would probably be OK. I wonder if 6" would be pushing it.

After sleeping on this, my inclination is to do what's easy first: lower the sump height in the skimmer area to 6", and decrease the difference between the primary and secondary drain to 0.5"

I'd only do this if it's necessary to be as cautious as I am, taking into account the loss of water from the tank AND the full emptying of the ATO bucket.

I also need to know if I should consider the secondary drain line at full volume to be a consideration. My guess is no, since if it ever is filled to anything less than a trickle, it would mean that this is due to a corresponding lowering of the volume of the sump.

Thanks.

 

[warrenmichaels]

Unfortunately, I can't edit my posts, so here's a revision of the above:

If I evaluate the following:
-Ignore any volume that might be in secondary line
-Consider the contributions of the DT, primary drain line, return line, 0.5 gal kalkwasser reservoir, 5 gal ATO
-Keep the skimmer chamber height at 6.5"

I can simply decrease the height difference between the primary and secondary drains to 0.5". This gives me a water reserve in the sump of 2.2 gallons if the ATO fails.

This seems like the simplest solution. Would this be wise?

 

[warrenmichaels]

Something worth mentioning in relation to this is that having a vertical height fluctuation of 0.5" in the DT without an overflow box would (it seems) require significantly more fluctuation in flow rate than would be needed if I were considering this height change within an overflow box.

The way I see it, if the amount of water flowing into an overflow changes by an eighth of an inch, corresponding to a tank volume fluctuation of o.4 gallons, the low volume of the box (half a gallon or so) would result in a significant height fluctuation with the overflow box. Therefore, it would make sense to have a much greater margin of vertical if using an overflow than not. Considering this, it seems that setting the primary and secondary drains 0.5" apart without an overflow would be reasonable.

Being a novice though, I really don't know.

 

[wrott]

What is your question?
You'll have to set-up any tank/sump and kill the power to see if it overflows and make adjustments accordingly--like drilling siphon breaks, etc...
5g ato is not much, you could use a 40g breeder for sump.

 

[warrenmichaels]

My question was what variable I should change in all this. A 40g breeder would be a better idea than the 20, so I don't know what I'll do.

I was able to juggle the parameters, and can make the 20 work if I have a height difference of 0.5" between the two outflows, and have 3.5 gal in the ATO.

Thanks.